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Body coordination during sit-to-stand in blind and sighted female children
Journal of Biomechanics xxx (xxxx) xxx
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Body coordination during sit-to-stand in blind and sighted female children Mozhgan Faraji Aylar a,⇑, Valdeci Carlos Dionisio b, AmirAli Jafarnezhadgero c, Ali Zolfaghari Parikhani d a
Faculty of Engineering, Electrical Engineering Department, Imam Reza International University, Mashhad, Iran Faculty of Physical Education and Physiotherapy, Federal University of Uberlândia, Minas Gerais, Brazil c Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran d Department of Business Administration, Faculty of Management, University of Applied Science and Technology (UAST), Tehran, Iran b
a r t i c l e
i n f o
Article history: Accepted 23 February 2020 Available online xxxx Keywords: Sit-to-stand Blind children Visuomotor processing Coordination Vector coding
a b s t r a c t Detecting coordination pattern and coordination variability help us to find how joints organize collaboratively to perform sit-to-stand (STS) under restricted visual input. This experiment aimed to compare the coordination of the trunk, hip, knee, and ankle and its variability between individuals with longand short-term restricted visual input during STS. Forty-five female children participated in this study, including fifteen congenitally blind (CB) children and 30 healthy children. The healthy children were divided randomly into two groups: one group in which the participants were instructed to keep their eyes open (EO) and another to keep their eyes closed (EC) for 20 min before the test. In the standing phase, CB children had a decreased ankle-knee vector angle on the nondominant (ND) side compared to that of healthy children. In the sagittal plane, a small coefficient-of-correspondences (CoC) was observed at seat-off (hip-trunk CoC on the dominant (D) side and ankle-hip CoC on the ND side) and in the preparation phase (ankle-hip CoC on the ND side and bilateral hip CoC). In the frontal plane (at the end: ankle-knee, in the standing phase: bilateral hip) a high CoC was observed (in the standing phase: knee-trunk CoC on the D side). The EC group had smaller CoCs at initiation event (knee-trunk and bilateral knee CoCs on both sides), the end event (ankle-knee and ankle-hip CoCs on the ND side), and in the standing phase (bilateral hip CoC) in the frontal plane than the other groups. The findings reveal that vector and CoC variables are altered because of long- and short-term restricted visual data and should be a focus in rehabilitation programs. Ó 2020 Published by Elsevier Ltd.
1. Introduction Coordination refers to the organization across multiple segments during movement. Evaluating coordination allows us to understand how various joints work together harmoniously and simultaneously maintain a balance to complete a functional activity. Some factors have led to poor coordination patterns, including aging (which has influence on the hip and ankle) (Hafer and Boyer, 2018), chronic ankle instability (in the hip and ankle in the sagittal and frontal planes) (Yen et al., 2017), neurological involvements (such as hemiparetic stroke (Lessard et al., 2017)) and orthopedic involvements (hip osteoarthritis) (Wallard et al., 2018). The coefficient-of-correspondence (CoC), measuring coordination variability, is reduced in all these conditions. Reducing coordination ⇑ Corresponding author at: Electrical Engineering Department, Imam Reza International University, Asrar St., Daneshgah Ave., Mashhad, Iran. E-mail address: [email protected] (M.F. Aylar).
variability has been suggested as a strategy to avoid movement errors when the balance is challenged (Yen et al., 2017). To maintain postural balance, it is necessary to integrate information from the visual, vestibular, and somatosensory systems (Sousa et al., 2012; Wikstrom et al., 2017). The data provided by the visual system play a paramount role in regulating postural orientation (Horak, 2006), while the somatosensory system prepares location and movement data about the body. It was observed in animal experiments that the early sensory deprivation induces functional higher compensation (Völgyi et al., 1993). In blind, it has been indicated that it would have a cross-modal manner to engaged the pieces of the visual cortex with other sensory conditions and the visual cortex could be recruited to a role in somatosensory processing (Cohen et al., 1997). This idea suggests that the short (i.e., eyes closed (EC) group) and long-term (i.e., congenitally blind (CB) children) restricted visual data could lead to different adaptations and also changes in the coordination.
https://doi.org/10.1016/j.jbiomech.2020.109708 0021-9290/Ó 2020 Published by Elsevier Ltd.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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M.F. Aylar et al. / Journal of Biomechanics xxx (xxxx) xxx
This experiment aimed to determine if the consolidation process occurs during rod intercept, or if it occurred only during long-term restricted visual input. The consolidation process for a new motor memory may take several hours (McGaugh, 2000) or, under certain conditions, minutes (IYa, 1998). This study tries to find more information about the process of dark adaptation for the visual system is adjusting to whole darkness or less levels of illumination. The time of rod intercept is less than or equal to 20 min, usually 8.2 min (Jackson and Edwards, 2008) and 12.5 min (Holfort et al., 2010), in young and older people, respectively. Sit-to-stand (STS) is a challenging functional task that needs the coordination of all body segments (Manckoundia et al., 2006) and the uninterrupted management of different sensory data; thus, STS performance is an indicator of mobility level (Souza et al., 2011). So, the function of the postural control system prevents falling and keeps postural stability during STS. Therefore, STS has been used to evaluate biomechanical variables in visual impairment ones (Aylar et al., 2019). Abnormal ankle (Aylar et al., 2016), knee, and hip (Aylar et al., 2018) kinematics have been observed in CB children when performing STS. When examining body movements of blind, it may be vital to consider not only the lower extremity joints but also the trunk. Specifically, it may be important to examine how blind individuals ‘‘coordinate” their lower and trunk segments during functional tasks. In addition, a previous study (Aylar et al., 2019) showed that the center-of-mass (COM) displacement of the nondominant (ND) foot segment and COM displacement of the dominant (D) leg segment were altered in blind individuals compared to healthy individuals. Therefore, the COM displacement of the foot and leg segments could affect the vector-angle components, and CB subjects showed less coordination variability than the other subjects. When sensorimotor control impairments are combined with long-term visual constraints, such as that in CB individuals, perhaps the memory of them could also provoke altered coordination of the lower extremity and trunk, and CB individuals can present lower CoCs than healthy individuals. However, few studies have explored this topic. The measure of vector angle and CoC of human bodies under restricted visual data during a highly challengeable task such as STS, needing complex and huge movement constraints, can show a critical step toward comprehending visual rehabilitative programs and interventions to improve physical functioning. Here, we aimed to analyze the coordination of the ankle, knee, hip, and trunk during STS (on both the D and ND sides) among CB, EC, and eyes open (EO) individuals. In addition, we hypothesized that the EC group would show a larger CoC of the ankle and hip than the CB group would.
2. Methods 2.1. Subjects Forty-five female children were recruited to participate in this study. The CB group included 15 females who had congenital blindness. The remaining 30 females were healthy and did not have any visual impairments. These 30 healthy individuals were divided into two different experimental condition groups. The participants in the EC group closed their eyes for 20 min before the STS test, while the subjects in the EO group kept their eyes open. The blind females were physically active in daily life and merely suffered from blindness. The eligibility criteria were to be female, be aged between 84 and 108 months, have no history of musculoskeletal or neuromuscular dysfunction such as flat feet or droop-
ing shoulders, have a BMI between 13 and 20 kg/m2 and be physically active in daily life. The participants were excluded if they presented any history of a ligament injury, surgery in either of the lower extremities, feelings of fatigue, a history of regular athletic training, the inability to complete the research protocol, a recent history of growth spurts that could affect the results, and participation in heavy physical tasks or exercise during the past two days. The dominant foot was determined to be the foot that was used to kick a ball. The study was approved by the local ethics committee (IR.ARUMS. REC.1396.259). 2.2. Data collection procedures Before performing the tests, the methods of using all of the equipment and instruments were demonstrated with a verbal explanation to the participants in the EO group and through the sense of touch for the EC and CB groups. The participants sat barefoot on a firm chair with no armrest, back support or wheels. The height of the chair was adjusted to 100% of each subject’s leg length, which was measured as the distance from the lateral femoral condyle to the ground. The participants sat with their bodies and lower extremities placed symmetrically relative to the chair, and the anterior-superior-iliac-spine (ASIS) width was determined as the distance between the feet. The subjects were instructed to raise their entire bodies from the chair at a selfselected velocity and to remain standing after reaching the upright position for 3 to 4 s (Kerr et al., 1994) with their arms folded across their chests. Each participant was asked to perform five STS trials, with 30 s of rest between trials, after having practiced three times before the recorded trials. Three events defined the STS task: (1) the initiation (In) of the movement, which was when the border of the acromion process marker moved forward in the sagittal plane, (2) the seat-off (SO) event, which was when knee extension began, and (3) the end (Ed) of STS, which was defined by the maximum height of the shoulder marker. According to these events, there were two phases: the preparation phase and the standing phase. Subjects’ joint kinematics were captured using an eight-camera 3D motion capture system, optoelectronic system (Qualisys AB, Sweden), with a sampling frequency of 100 Hz. The motion capture data were filtered using a fourth-order Butterworth filter with a cutoff frequency of 10 Hz by using MATLAB R2015a software. The kinematic values were recorded along the vertical (Z), mediolateral (Y), and anteroposterior (X) directions. The positive sagittal (anterioposterior) axis was the direction of the forward movement, and the positive frontal (mediolateral) axis was directed to the ND side while the positive vertical axis was directed upward. Retroreflective markers were placed over bony landmarks, including the vertex, seventh-cervical-vertebra (C7), and the spinous process of the twelfth-thoracic-vertebrae. Markers were also placed bilaterally on the lateral borders of the acromion process, greater humeral tubercle, olecranon process of the ulna, head of the styloid process of the ulna, ASIS, posterior-superior-iliac-spine (PSIS), greater trochanter, lateral femoral epicondyle, lateral malleolus, 5th metatarsal head, and calcaneal tuberosity. Markers on the olecranon process of the ulna and head of the styloid process of the ulna were used to monitor the arms folded across the chest. Seven segments were defined to create biomechanical models by retroreflective markers. The markers used on lateral malleoli, 5th distal metatarsal head, and calcaneal tuberosity for build ankle (bilaterally). The markers used on center of the foot and the lateral femoral epicondyle for build the knee (bilaterally). The markers used on center of the leg and the center of the pelvis created by the ASIS, PSIS, and greater trochanter for build the hip (bilaterally). The markers on midpoint of the two pelvis and the midpoint of the
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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M.F. Aylar et al. / Journal of Biomechanics xxx (xxxx) xxx
two shoulder markers (lateral border of the acromion process and head of the humerus) for build the trunk.
ai ¼
The outcome variables were coordination of the ankle, knee, hip, and trunk in the frontal and sagittal planes during four STS cycles. In this study, a vector coding technique (Robertson et al., 2014) was used to quantify coordination of the ankle, knee, hip, and trunk. The coupling angle h, or the relative motion between two segments, was used to calculate the orientation of consecutive frames on the angle-angle diagram (Fig. 4 shows the angle-angle diagram of a normal subject during STS) relative to the right horizontal:
ð1Þ
where 0° h 360°, i indicates consecutive data points in a cycle, and j identifies the four STS cycles. Four angle-angle diagrams over each STS were constructed with (1) the ankle angle on the a-axis and the knee, hip, and trunk angles on the b-axis, (2) the knee angle on the a-axis and the hip and trunk angles on the b-axis, and (3) the hip angle on the a-axis and the trunk angle on the b-axis. Since these angles are directional and obtained from polar distributions (0°-360°), taking the arithmetic mean of a series of angles can result in errors in the average value and incorrect representation of the orientation of the vectors by the average val-
2 1 2 2 ri ¼ bi þ ai
ues. Therefore, mean coupling angles (hi ) must be computed using
circular statistics. hi is calculated within a subject and then across a group from the mean horizontal (bi ) and vertical (ai ) components:
n 1X cos hj;i n j¼1
ð2Þ
ð4Þ
Moreover, it has a well-defined angle with respect to the positive horizontal axis. This angle is referred to as the coupling angle h. The mean coupling angle across the four STS cycles is again defined:
hi ¼
8 > > > <
tan1
ai
if X i > 0
bi
> > 1 > : 180 þ tan
ai
ð5Þ
if X i < 0
bi
The vector coding analysis can provide a measure of the coordination pattern. A vector angle has a value ranging from 0° to 360°. Fig. 1 shows what the vector angles of the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, hip-trunk, D ankle-ND ankle, D knee-ND knee, and D hip-ND hip indicate when they appear in each of the quadrants during STS. Additionally, descriptions of the coordination patterns in terms of 0, 45, 90, 135, 180, 225, 315, and 360 degrees of the above mentioned variables are shown in Fig. 2 (sagittal plane) and Fig. 3 (frontal plane) (see Fig. 4). The CoC (Yen et al., 2017) was calculated as:
!
CoC ¼ r i 1
bi ¼
ð3Þ
The length of the mean vector is then defined as
2.3. Outcome variables and data analysis
aj;iþ1 aj;i hj;i ¼ tan1 bj;iþ1 bj;i
n 1X sin hj;i n j¼1
rðmaxriðri ÞÞ rmax
ð6Þ
where max (ri) is the maximum vector length for the maximum possible vector length observed at each respective interval over the four selected STS cycles, r is the standard deviation, and rmax was calculated using the following formula:
rmax
1 ¼ 2
rffiffiffiffiffiffiffiffiffiffiffiffiffi N N1
ð7Þ
Fig. 1. Relationship between phase angle in each quadrant and ankle-knee (A and J), ankle-hip (D and M), ankle-trunk (G and P), knee-hip (B and K), knee-trunk (E and N), hip-trunk (H and Q), D ankle-ND ankle (C and L), D knee-ND knee (F and O), and D hip-ND hip (I and R) relative motion in sagittal (A, B, C, D, E, F, G, H, and I) and frontal (J, K, L, M, N, O, P, Q, and R) planes. Abbreviations: D, dominant side; ND, nondominant side; LFR, lateral flexion to the right; LFL, lateral flexion to the left.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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M.F. Aylar et al. / Journal of Biomechanics xxx (xxxx) xxx
Fig. 2. Description of the coordination pattern values in each quadrant and movement of segments (ankleknee (A), ankle-hip (B), ankle-trunk (C), knee-hip (D), knee-trunk (E), hip-trunk (F), D ankle-ND ankle, D knee-ND knee, and D hip-ND hip (G)) relative together during sit-to-stand in sagittal plane. Abbreviations: D, dominant side; ND, nondominant side.
Fig. 3. Description of the coordination pattern values in each quadrant and movement of segments (ankleknee (A), ankle-hip (B), ankle-trunk (C), knee-hip (D), knee-trunk (E), hip-trunk (F), D ankle-ND ankle, D knee-ND knee, and D hip-ND hip (G)) relative together during sit-to-stand in frontal plane. Abbreviations: D, dominant side; ND, nondominant side; LFR, lateral flexion to the right; LFL, lateral flexion to the left.
where N is the number of cycles. Note Eq. (7) is only accurate for an array with an even number of normalized samples. The CoC measures the consistency of relative segment motions in a given limb. A large CoC represents high variability of the STS pattern.
standard deviation of groups. In addition, we interpreted the effect size as trivial (d < 0.2), small (0.2 to <0.5), moderate (0.5 and <0.8), or large (0.8). 3. Results
2.4. Statistical analysis A multivariate-analysis-of-variance (MANOVA) test with Bonferroni’s post hoc test was used for between-group comparisons. Additionally, ‘‘P” stands for MONOVA, and ‘‘p” stands for a significant interaction between group and condition. The alpha level was set at p < (0.05/number of parameters). Statistical analysis was performed using SPSS 19.0Ò software. The effect sizes (d) were calculated as a ratio of the mean difference divided by the mean to the
There were no significant differences between the groups in age, mass, height, leg length, and ASIS width (Table 1). On both sides, the vector-angle values of the ankle-knee, anklehip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk pairs for all groups were similar in the sagittal (P = 0.610) and frontal (P = 0.670) planes during all events (Table 2). The CoC of the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk pairs in the sagittal plane showed a
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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M.F. Aylar et al. / Journal of Biomechanics xxx (xxxx) xxx
Fig. 4. The angle-angle diagram (ankle-knee (A and J), ankle-hip (D and M), ankle-trunk (G and P), kneehip (B and K), knee-trunk (E and N), hip-trunk (H and Q), D ankle-ND ankle (C and L), D knee-ND knee (F and O), and D hip-ND hip (I and R)) of a normal subject during sit-to-stand in sagittal (A, B, C, D, E, F, G, H, and I) and frontal (J, K, L, M, N, O, P, Q, and R) planes. Abbreviations: D, dominant side; ND, nondominant side.
Table 1 Demographic characteristics of subjects. Groups
N Mass (kg) Height (m) BMI Leg length (cm) ASIS width (cm) Age (month) Gender Foot dominant side Hand dominant side
Sig.
Congenital blindness
Eyes closed
Eyes open
15 25.6 (2.0) 1.3 (0.0) 16.0 (2.5) 36.5 (1.6) 17.8 (1.1) 94.6 (5.6) Female Right Right
15 24.2 (1.3) 1.1 (0.0) 15.7 (0.8) 34.6 (1.1) 15.7 (0.5) 93.8 (5.9) Female Right Right
15 26.1 (5.1) 1.3 (0.0) 16.0 (2.0) 36.2 (1.5) 16.5 (0.9) 95.8 (5.4) Female Right Right
NA 0.641 0.632 0.912 0.100 0.250 0.856 NA 0.756 NA
Values are mean (standard deviation). Abbreviations: N, number of subjects; NA, not applicable; BMI, body mass index; ASIS, Anterior superior iliac spine.
significant interaction between group and condition at the SO (P = 0.000) and Ed (P = 0.000) events. Hip-trunk CoC (p = 0.002, d = 0.95) on the D side and ankle-hip CoC (p < 0.001, d = 2.18) on the ND side were significantly lower in the CB group than in the EO group at the SO. The ankle-trunk and knee-trunk CoCs were significantly greater in the EC group than in the CB group on the D (p < 0.001, d = 3.40; p < 0.001, d = 3.30) and ND (p < 0.001, d = 3.39; p < 0.001, d = 3.30) sides during the Ed. On the ND side, the EC group presented a greater hip-trunk CoC than the CB group at the Ed (p = 0.029, d = 3.07). Additionally, the CoC in the frontal plane demonstrated a significant interaction between group and condition at the In (P = 0.000), SO (P = 0.000), and Ed (P = 0.000) events. The knee-trunk CoC of the EC group was significantly lower than that of the EO group on the D (p < 0.001, d = 2.10) and ND (p = 0.003, d = 1.61) sides at the In. On the D side, the EC group presented a greater ankle-hip CoC than the CB group at the SO (p < 0.001, d = 2.60). On the ND side, the ankle-knee (p = 0.003, d = 1.67) and ankle-hip (p = 0.002, d = 1.76) CoCs in the EC group were significantly lower than those in the EO group at the Ed. The ankle-knee CoC in the CB group was significantly less than that in the EO group (p = 0.001, d = 1.76). Other variables on both sides were similar among the groups at all events (Table 3). The ankle-knee vector angle in the sagittal plane demonstrated a significant interaction between group and condition in the standing phase (P = 0.015). On the ND side, the ankle-knee vector angle
of the CB group was significantly lower than that of the EO group (p < 0.001, d = 1.48) (Fig. 5B). The CoC measures in the sagittal plane showed a significant interaction between group and condition in the preparation phase (P = 0.002). The ankle-hip CoC of the CB group was significantly lower than that of the EO group (p = 0.003, d = 1.43) on the ND side (Fig. 5F). Furthermore, the knee-trunk CoC in the frontal plane demonstrated a significant interaction between group and condition in the standing phase (P = 0.000). On the D side, the knee-trunk CoC in the CB group was significantly greater than that in the EO group (p < 0.001, d = 1.60) (Fig. 5G). Other variables on both sides were similar among the groups (Fig. 5A, C, D, E, and H). The D ankle-ND ankle, D knee-ND knee, and D hip-ND hip vector angles (Fig. 6A and B) in both planes were similar among the groups. The D hip-ND hip CoC in the sagittal plane demonstrated a significant interaction between group and condition in the preparation phase (P = 0.005). D hip-ND hip CoC in the CB group was significantly less than that in the EO group (p = 0.011, d = 1.08) (Fig. 6C). Additionally, the D knee-ND knee and D hip-ND hip CoCs in the frontal plane showed a significant interaction between group and condition at the In event (P = 0.007) and in the standing phase (P = 0.004), respectively. The D knee-ND knee CoC in the EC group was significantly less than that in the EO group (p = 0.009, d = 1.42) at In. The D hip-ND hip CoCs for the CB group (p = 0.003, d = 1.27) and EC group (p = 0.001, d = 1.26) were
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Table 2 Congenitally blind (CB), eyes closed (EC), and eyes open (EO) children’s ankle-knee (AK), ankle-hip (AH), ankle-trunk (AT), knee-hip (KH), knee-trunk (KT), and hip-trunk (HT) coordination patterns in the sagittal and frontal planes during initiation (In), seat-off (SO), and end (Ed) events in dominant (D) and non-dominant sides. Side
Group
Sagittal plane D CB
EC
EO
ND
CB
EC
EO
Frontal plane D CB
EC
EO
ND
CB
EC
EO
Event
Vector angle (deg) AK
AH
AT
KH
KT
HT
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
166.9 (108.2) 126 (48) 240 (2.2) 156.6 (112.6) 107.1 (47.3) 241.5 (1.3) 162 (102.2) 117.4 (38.4) 240.9 (1.4) 118.6 (70.3) 103.6 (23) 240.4 (1.6) 142.7 (112.2) 115.2 (30.3) 240.8 (1.9) 109.8 (91.9) 136.8 (48.6) 240.6 (0.9)
271.9 (20) 186.5 (78.3) 236.6 (11.6) 250.4 (70.5) 232.8 (72.5) 240.3 (7.5) 271.6 (26.1) 238.1 (51.7) 241.7 (1.3) 248.5 (55.5) 172.2 (81.7) 235.4 (16.4) 264.8 (40.8) 223.8 (63.7) 240.4 (2.2) 259.4 (46.2) 237 (51.2) 240.8 (1.4)
109.2 (67.2) 121.8 (64.5) 172 (45) 109.1 (65.7) 109 (68.9) 135.5 (2.3) 113.8 (68.4) 110.8 (35.9) 159.1 (40.7) 114.6 (66.8) 130.4 (68) 170.9 (45.6) 92.5 (35.1) 118 (66.7) 136.3 (2.7) 112.5 (64.9) 109.7 (28.6) 160.6 (40.6)
275 (13.1) 179.4 (138.2) 222.2 (10.3) 268.9 (42.5) 218.6 (127.1) 224 (7.1) 272.7 (12.5) 261.4 (85) 225.8 (0.7) 264.1 (53.7) 145.6 (136.1) 221.1 (13) 259.4 (50.8) 245.3 (116) 224.3 (1) 264.5 (53.3) 258.5 (79.4) 225 (1.4)
111.1 (65.2) 93 (101.6) 174.1 (29.5) 94.3 (44.1) 87.9 (75.6) 152.1 (1.3) 112.8 (65.1) 91.1 (73.3) 166.8 (26.1) 108.8 (66) 84.6 (102.2) 173.9 (29.1) 100.8 (55) 87.4 (76.4) 152.1 (1.2) 108.9 (65.8) 91.8 (70.5) 167.3 (26)
151.2 (48.3) 127.3 (99.9) 178.6 (35.6) 141.4 (44.4) 132.1 (65.6) 150.9 (8) 152.6 (48) 132.5 (66.8) 166.9 (25.3) 139.8 (58.9) 112.2 (102.7) 173.5 (38) 149.3 (52.2) 129.5 (67.6) 151.7 (1) 145 (53.6) 132.3 (68) 166.9 (25.6)
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
145.9 (103) 125.4 (83.1) 232.7 (4.3) 186.3 (117.3) 111.1 (77.6) 233.2 (4.8) 119.5 (97.6) 127 (82.6) 233 (4.4) 154 (118.8) 158.8 (78.2) 233.9 (4.2) 173.6 (101.2) 169.1 (73.7) 231 (4) 168.1 (116) 189 (101.9) 229.6 (3.4)
176.9 (106.5) 150.8 (98.1) 227.5 (13.5) 228 (102.7) 115.2 (85.4) 229 (11.4) 140.8 (106.2) 135.4 (86) 233 (4.2) 144.1 (118.5) 197.6 (82.2) 229.6 (10.3) 209.5 (103.3) 161.7 (68.7) 230.4 (4.3) 141.2 (114.7) 192.5 (105.5) 229.6 (3.5)
142 (107.2) 147.2 (117.3) 178 (0.9) 177.7 (128.5) 199 (117.3) 177.2 (2.4) 157.6 (133) 141.3 (98.2) 178.1 (0.5) 195.8 (125.2) 193.1 (100.9) 177.9 (1) 198.4 (109.6) 180.2 (82.1) 177.3 (2.6) 180.6 (128.7) 122.1 (92.6) 178.3 (0.4)
150.6 (120.2) 133.7 (112.5) 220.2 (11.5) 174.6 (107.7) 60.4 (60.5) 221.1 (9.6) 130.6 (105.1) 145.8 (105.1) 224.8 (0.5) 155.9 (105.6) 202 (127.1) 221 (9.6) 174.3 (105.9) 108.5 (87.5) 224.3 (1.2) 144.5 (98.4) 129.9 (86.2) 224.8 (0.3)
126.1 (122.5) 131 (133.4) 178.5 (0.6) 161.6 (122.7) 217.7 (153.4) 178.1 (2.7) 150.2 (138.1) 112.4 (113.4) 178.5 (0.3) 166.2 (124) 195.3 (140.1) 178.5 (0.6) 165.3 (114.3) 201.8 (120.8) 177.8 (2.2) 161.6 (122.6) 125.8 (107.2) 178.5 (0.3)
151.2 (117.7) 159.6 (135.3) 177.7 (2.1) 167.1 (98.2) 216.5 (148.9) 176.8 (4.5) 173.6 (139.9) 138 (126.9) 178.5 (0.3) 175.1 (116.2) 161.3 (97.4) 178.1 (1.3) 154.2 (96.9) 195.3 (133) 177.7 (2.6) 190.6 (127) 119.7 (109.3) 178.5 (0.3)
Values are mean (standard deviation).
significantly lower than that of the EO group in the standing phase (Fig. 6D).
4. Discussion The results showed that the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk vector angles for all groups in the sagittal plane on both sides were similar during all events and phases. Compared with healthy children, CB children presented more ankle motion on the ND side in plantar flexion relative to knee motion in extension. The altered ankle-knee vector angle in CB children may be led to the altered COM in these segments. Our previous study (Aylar et al., 2019) detected that COM displacements of the foot and leg were different among groups in the anteroposterior direction. Therefore, altered vector-angle components may be associated with the foot COM and leg COM. Additionally, the CB individuals showed less coordination variability in the sagittal plane than EO subjects at the SO event (hip-trunk on D side and ankle-hip on ND side) and in the preparation phase (ankle-hip on ND side). The SO event is a vital point (the most unstable moment) of STS, where the total load is transferred to the feet and the COM creates an external moment at the knee (Hughes et al., 1994). Moreover, among all segments, the head-arms-trunk (HAT) segment generates the most horizontal momentum of the
whole body-center-of-mass (BCOM), and rotation of the thigh about the knee joint is the main contributor to vertical momentum generation (Riley et al., 1991). Therefore, CB children’s locomotory system may consistently regulate the ankle-hip and hip-trunk coordination as an altered strategy to reduce the possibility of making a movement error when the balance is challenged. In this experiment, the CoCs of the mentioned parameters in the EO group were higher than those in the other groups. These results suggest that healthy individuals have more movement variability. Then, reducing variability is a possible strategy to reduce errors in movement, and this strategy is optimal for the CB group; however, less variability is not necessarily a favorable movement strategy. Furthermore, the EC group demonstrated higher coordination variability than the CB group at Ed (ankle-trunk and knee-trunk on both sides and hip-trunk on the ND side). The CB children’s locomotor systems were able to perform the STS under the deprivation of visual input for 94 months, but EC children only had deprivation of visual input for 20 min. Long-term deprivation of visual input may be influenced by an individual’s habitual activity, so it is reasonable that CB children had more limitations to their activity than did others. This concept can explain why the EC group had higher coordination variability than the CB group in the sagittal plane. The CB group increased their consistency to better control their balance during the challenging task, but the EC group did not adopt this strategy to decrease errors in their STS performance. This result
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Table 3 Coordination variability in different STS events in the sagittal and frontal planes for Congenitally blind (CB), eyes closed (EC), and eyes open (EO) groups in dominant (D) and nondominant (ND) sides. Side
Sagittal plane D
Group
CB
EC
EO
ND
CB
EC
EO
Frontal plane D
CB
EC
EO
ND
CB
EC
EO
Event
Coefficient of correspondence (CoC) AK
AH
AT
KH
KT
HT
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
0.4 (0.3) 0.7 (0.3) 1 (0) 0.4 (0.3) 0.7 (0.2) 1 (0) 0.4 (0.3) 0.8 (0.3) 1 (0) 0.5 (0.2) 0.9 (0.1) 1 (0) 0.3 (0.2) 0.8 (0.2) 1 (0) 0.5 (0.3) 0.7 (0.4) 1 (0)
1 (0.1) 0.2 (0.3) 1 (0) 0.9 (0.2) 0.3 (0.3) 1 (0) 0.9 (0.1) 0.7 (0.4) 1 (0) 0.8 (0.4) 0.1 (0.2)* 1 (0.1) 0.8 (0.4) 0.5 (0.4) 1 (0) 0.8 (0.4) 0.7 (0.3) 1 (0)
0.8 (0.4) 0.7 (0.4) 0.7 (0.2) 0.9 (0.2) 0.7 (0.3) 1 (0)** 0.6 (0.5) 0.8 (0.3) 0.8 (0.2) 0.7 (0.4) 0.7 (0.4) 0.6 (0.2) 0.8 (0.3) 0.9 (0.2) 1 (0)** 0.6 (0.5) 0.9 (0.2) 0.8 (0.2)
1 (0) 0.5 (0.3) 1 (0) 0.8 (0.3) 0.7 (0.2) 1 (0) 1 (0) 0.7 (0.3) 1 (0) 0.8 (0.4) 0.5 (0.2) 1 (0) 0.8 (0.4) 0.7 (0.3) 1 (0) 0.8 (0.4) 0.6 (0.4) 1 (0)
0.8 (0.4) 0.7 (0.2) 0.8 (0.1) 0.8 (0.4) 0.9 (0.1) 1 (0)** 0.6 (0.5) 0.9 (0.1) 0.9 (0.1) 0.8 (0.4) 0.8 (0.2) 0.8 (0.1) 0.8 (0.3) 0.9 (0.1) 1 (0)** 0.6 (0.5) 0.8 (0.2) 0.9 (0.1)
0.8 (0.3) 0.5 (0.3)* 0.8 (0.2) 0.8 (0.4) 0.7 (0.3) 1 (0) 0.7 (0.4) 0.8 (0.3) 0.9 (0.1) 0.7 (0.3) 0.5 (0.2) 0.8 (0.2) 0.8 (0.4) 0.7 (0.3) 1 (0)** 0.6 (0.4) 0.7 (0.4) 0.9 (0.1)
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
0.5 (0.3) 0.5 (0.3) 1 (0) 0.3 (0.2) 0.6 (0.3) 1 (0) 0.6 (0.3) 0.4 (0.3) 1 (0) 0.5 (0.4) 0.4 (0.3) 0.9 (0)* 0.4 (0.4) 0.5 (0.3) 0.9 (0)* 0.5 (0.3) 0.3 (0.2) 1 (0)
0.4 (0.4) 0.2 (0.1) 1 (0.1) 0.4 (0.3) 0.6 (0.2)** 1 (0) 0.6 (0.3) 0.4 (0.3) 1 (0) 0.5 (0.4) 0.4 (0.3) 1 (0) 0.6 (0.4) 0.5 (0.4) 0.9 (0)* 0.5 (0.4) 0.2 (0.2) 1 (0)
0.5 (0.4) 0.3 (0.4) 1 (0) 0.3 (0.3) 0.2 (0.1) 1 (0) 0.5 (0.4) 0.4 (0.4) 1 (0) 0.5 (0.4) 0.2 (0.4) 1 (0) 0.4 (0.4) 0.5 (0.4) 1 (0) 0.5 (0.4) 0.1 (0.2) 1 (0)
0.4 (0.3) 0.7 (0.3) 1 (0) 0.4 (0.4) 0.8 (0.4) 1 (0) 0.6 (0.3) 0.4 (0.3) 1 (0) 0.1 (0.1) 0.5 (0.2) 1 (0) 0.3 (0.3) 0.4 (0.4) 1 (0) 0.3 (0.4) 0.4 (0.4) 1 (0)
0.4 (0.4) 0.8 (0.4) 1 (0) 0.2 (0.2)* 0.8 (0.4) 1 (0) 0.7 (0.3) 0.4 (0.4) 1 (0) 0.2 (0.2) 0.4 (0.4) 1 (0) 0.1 (0.1)* 0.3 (0.4) 1 (0) 0.5 (0.4) 0.5 (0.4) 1 (0)
0.3 (0.4) 0.4 (0.4) 1 (0) 0.4 (0.3) 0.7 (0.3) 1 (0) 0.4 (0.4) 0.4 (0.4) 1 (0) 0.2 (0.1) 0.3 (0.4) 1 (0) 0.4 (0.4) 0.4 (0.4) 1 (0) 0.3 (0.4) 0.3 (0.4) 1 (0)
Values are mean (standard deviation). Abbreviations: AK, ankle-knee; AH, ankle-hip; AT, ankle-trunk; KH, knee-hip; KT, knee-trunk; HT, hip-trunk; In, initiation; SO, seat-off; Ed, end; STS, sit-to-stand. * When compared to the eyes open group (p < 0.05). ** When compared to the congenitally blind group (p < 0.05).
suggests that fewer CoCs that were reported were optimal to manage a hard task in CB children. In the frontal plane, the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk vector angles of all groups were similar. This result indicates that the ankle, knee, hip, and trunk move harmoniously in the frontal plane during STS, and short- or long-term restriction of visual input does not influence these parameters. However, the EC group had less variability relative to the EO group at the In (knee-trunk on both sides) and Ed (ankle-knee and ankle-hip on ND side) events. A previous study demonstrated that less ankle-hip coordination variability is associated with chronic-ankle-instability (CAI) in the frontal plane (Yen et al., 2017), and the authors assumed it to be a preventative strategy for reducing future injuries of involved segments and controlling balance among subjects with CAI. The knee initiates movement at the In event, so the reductions in the knee-trunk and ankle-knee CoCs suggest that these segments maintain their consistency to start STS successfully. Moreover, the ankle-hip pair of the EC group showed great coordination variability compared to that of the CB group on the ND side during SO. This condition was explained for the sagittal plane, but unfortunately, there are a limited number of studies on the CoC in the frontal plane. Compared with the EO group, the CB group presented high variability of the
knee-trunk pair on the D side in the standing phase. However, at Ed, the CB group had less variability in the ankle-knee pair on the ND side. The results suggested that long-term restricted visual memory has a significant impact on knee-trunk coordination during the standing phase and may predispose individuals to future injuries of the involved limbs. On the other hand, the low ankleknee CoC of the CB group was a preventative strategy to avoid injuries. Comparing the D and ND sides, the vector angle and CoC of the ankle, knee, and hip in the sagittal plane were similar, suggesting good bilateral coordination of the lower extremity during STS, although there was time-restricted visual input for subjects. However, during the preparation phase, the D hip-ND hip CoC of the CB group was lower than that of the EO group. The interlimb adaptations in hip segments of CB children indicated that long-term restricted visual memory has led to consistency among subjects. Generally, a difference in interlimb variables is a consequence of an injury (Haddad et al., 2006). The motor control system of CB children may alter the coordination between the individual limbs to adapt to the long-term restricted visual condition. Also, the presented results in the study can be different for male children (Bates et al., 2016; Bruening et al., 2015; Jenkins et al., 2017), but it deserves more investigations.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Fig. 5. Coordination pattern (A, B, C, and D) and coordination variability (E, F, G, and H) in sagittal (A, B, E, and F) and frontal (C, D, G, and H) planes on dominant (A, C, E, and G) and non-dominant (B, D, F, and H) sides among the congenitally blind, eyes closed, and eyes open groups during preparation phase (PP) and standing phase (SP). Bars represent standard deviations. *: When compared to the eyes open group (p < 0.05).
The vector angles and CoCs of the D side of the lower limb joints with its ND sides in the frontal plane were similar among individuals during events. The exceptions were the lower D knee-ND knee CoC of the EC group at In and the lower D hip-ND hip CoCs of the EC and CB groups than those of the EO group in the standing phase. They indicated that bilateral consistency occurred in the hip of the CB group in the standing phase and in the knee and hip of the EC group at the In event and in the standing phase, respectively. We were not able to find other studies addressing these issues. In general, the results showing that the human body continuously tries to reach optimal coordination. Finally, the restricted
visual input was shown to have considerable influence on the coordination pattern in the standing phase and on coordination variability at all events and phases. These results indicate that visual memory cannot change the coordination pattern of the STS, but the coordination variability of this movement is highly influenced by the duration visual data is restricted. The number of subjects in the present investigation was relatively small; however, this study had sufficient statistical power to detect between-group differences. Further studies are suggested to combine the values of joint torques with muscle activities during STS.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Fig. 6. The control and experimental groups’ D ankle-ND ankle, D knee-ND knee, D hip-ND hip coordination pattern (A and B) and variability (C and D) in the sagittal (A and C) and frontal planes (B and D) in all events and phases of sit-to-stand. Bars represent standard deviations. Abbreviations: D, dominant side; ND, non-dominant side; In, initiation; SO, seat-off, Ed, end; PP, preparation phase; SP, standing phase. *: When compared to the eyes open group (p < 0.05).
5. Conclusion The results of this study indicated that the consolidation process occurred not only for trunk but also for the lower extremities. In the sagittal plane, the CB individuals presented difficulties in the ankle-knee coordination pattern parameters on the nondominant side (at standing phase). In this plane, their dominant side of hip-trunk (at seat-off), and nondominant side of ankle-hip (at seat-off and in the preparation phase); in the frontal plane, their nondominant side of ankle-knee (at the end) coordination variability parameters were less than the EO group. However, they had greater knee-trunk coordination variability relative to the EO group on the dominant side during the standing phase in the frontal plane. Hence, this investigation recommends that the design of rehabilitation programs should focus on the amendment of blind individuals’ strategies to prevent future injuries among them. Acknowledgments We thank all of the individuals who participated in the study. References Aylar, M.F., Dionisio, V.C., Jafarnezhadgero, A., 2019. Do the center of mass strategies change with restricted vision during the sit-to-stand task?. Clin. Biomech. 62, 104–112. https://doi.org/10.1016/j.clinbiomech.2019.01.011. Aylar, M.F., Firouzi, F., Araghi, M.R., 2016. Influence of time restriction, 20 minutes and 94.6 months, of visual information on angular displacement during the sitto-stand (STS) task in three planes. J. Phys. Therapy Sci. 28 (12), 3330–3336. https://doi.org/10.1589/jpts.28.3330. Aylar, M.F., Jafarnezhadgero, A.A., Esker, F.S., 2018. Sit-to-stand ground reaction force characteristics in blind and sighted female children. Gait & Posture 62, 34– 40. https://doi.org/10.1016/j.gaitpost.2018.03.004. Bates, N.A., Nesbitt, R.J., Shearn, J.T., Myer, G.D., Hewett, T.E., 2016. Sex-based differences in knee ligament biomechanics during robotically simulated athletic tasks. J. Biomech. 49 (9), 1429–1436. https://doi.org/10.1016/j.jbiomech. 2016.03.001.
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Body coordination during sit-to-stand in blind and sighted female children Mozhgan Faraji Aylar a,⇑, Valdeci Carlos Dionisio b, AmirAli Jafarnezhadgero c, Ali Zolfaghari Parikhani d a
Faculty of Engineering, Electrical Engineering Department, Imam Reza International University, Mashhad, Iran Faculty of Physical Education and Physiotherapy, Federal University of Uberlândia, Minas Gerais, Brazil c Faculty of Educational Sciences and Psychology, University of Mohaghegh Ardabili, Ardabil, Iran d Department of Business Administration, Faculty of Management, University of Applied Science and Technology (UAST), Tehran, Iran b
a r t i c l e
i n f o
Article history: Accepted 23 February 2020 Available online xxxx Keywords: Sit-to-stand Blind children Visuomotor processing Coordination Vector coding
a b s t r a c t Detecting coordination pattern and coordination variability help us to find how joints organize collaboratively to perform sit-to-stand (STS) under restricted visual input. This experiment aimed to compare the coordination of the trunk, hip, knee, and ankle and its variability between individuals with longand short-term restricted visual input during STS. Forty-five female children participated in this study, including fifteen congenitally blind (CB) children and 30 healthy children. The healthy children were divided randomly into two groups: one group in which the participants were instructed to keep their eyes open (EO) and another to keep their eyes closed (EC) for 20 min before the test. In the standing phase, CB children had a decreased ankle-knee vector angle on the nondominant (ND) side compared to that of healthy children. In the sagittal plane, a small coefficient-of-correspondences (CoC) was observed at seat-off (hip-trunk CoC on the dominant (D) side and ankle-hip CoC on the ND side) and in the preparation phase (ankle-hip CoC on the ND side and bilateral hip CoC). In the frontal plane (at the end: ankle-knee, in the standing phase: bilateral hip) a high CoC was observed (in the standing phase: knee-trunk CoC on the D side). The EC group had smaller CoCs at initiation event (knee-trunk and bilateral knee CoCs on both sides), the end event (ankle-knee and ankle-hip CoCs on the ND side), and in the standing phase (bilateral hip CoC) in the frontal plane than the other groups. The findings reveal that vector and CoC variables are altered because of long- and short-term restricted visual data and should be a focus in rehabilitation programs. Ó 2020 Published by Elsevier Ltd.
1. Introduction Coordination refers to the organization across multiple segments during movement. Evaluating coordination allows us to understand how various joints work together harmoniously and simultaneously maintain a balance to complete a functional activity. Some factors have led to poor coordination patterns, including aging (which has influence on the hip and ankle) (Hafer and Boyer, 2018), chronic ankle instability (in the hip and ankle in the sagittal and frontal planes) (Yen et al., 2017), neurological involvements (such as hemiparetic stroke (Lessard et al., 2017)) and orthopedic involvements (hip osteoarthritis) (Wallard et al., 2018). The coefficient-of-correspondence (CoC), measuring coordination variability, is reduced in all these conditions. Reducing coordination ⇑ Corresponding author at: Electrical Engineering Department, Imam Reza International University, Asrar St., Daneshgah Ave., Mashhad, Iran. E-mail address: [email protected] (M.F. Aylar).
variability has been suggested as a strategy to avoid movement errors when the balance is challenged (Yen et al., 2017). To maintain postural balance, it is necessary to integrate information from the visual, vestibular, and somatosensory systems (Sousa et al., 2012; Wikstrom et al., 2017). The data provided by the visual system play a paramount role in regulating postural orientation (Horak, 2006), while the somatosensory system prepares location and movement data about the body. It was observed in animal experiments that the early sensory deprivation induces functional higher compensation (Völgyi et al., 1993). In blind, it has been indicated that it would have a cross-modal manner to engaged the pieces of the visual cortex with other sensory conditions and the visual cortex could be recruited to a role in somatosensory processing (Cohen et al., 1997). This idea suggests that the short (i.e., eyes closed (EC) group) and long-term (i.e., congenitally blind (CB) children) restricted visual data could lead to different adaptations and also changes in the coordination.
https://doi.org/10.1016/j.jbiomech.2020.109708 0021-9290/Ó 2020 Published by Elsevier Ltd.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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This experiment aimed to determine if the consolidation process occurs during rod intercept, or if it occurred only during long-term restricted visual input. The consolidation process for a new motor memory may take several hours (McGaugh, 2000) or, under certain conditions, minutes (IYa, 1998). This study tries to find more information about the process of dark adaptation for the visual system is adjusting to whole darkness or less levels of illumination. The time of rod intercept is less than or equal to 20 min, usually 8.2 min (Jackson and Edwards, 2008) and 12.5 min (Holfort et al., 2010), in young and older people, respectively. Sit-to-stand (STS) is a challenging functional task that needs the coordination of all body segments (Manckoundia et al., 2006) and the uninterrupted management of different sensory data; thus, STS performance is an indicator of mobility level (Souza et al., 2011). So, the function of the postural control system prevents falling and keeps postural stability during STS. Therefore, STS has been used to evaluate biomechanical variables in visual impairment ones (Aylar et al., 2019). Abnormal ankle (Aylar et al., 2016), knee, and hip (Aylar et al., 2018) kinematics have been observed in CB children when performing STS. When examining body movements of blind, it may be vital to consider not only the lower extremity joints but also the trunk. Specifically, it may be important to examine how blind individuals ‘‘coordinate” their lower and trunk segments during functional tasks. In addition, a previous study (Aylar et al., 2019) showed that the center-of-mass (COM) displacement of the nondominant (ND) foot segment and COM displacement of the dominant (D) leg segment were altered in blind individuals compared to healthy individuals. Therefore, the COM displacement of the foot and leg segments could affect the vector-angle components, and CB subjects showed less coordination variability than the other subjects. When sensorimotor control impairments are combined with long-term visual constraints, such as that in CB individuals, perhaps the memory of them could also provoke altered coordination of the lower extremity and trunk, and CB individuals can present lower CoCs than healthy individuals. However, few studies have explored this topic. The measure of vector angle and CoC of human bodies under restricted visual data during a highly challengeable task such as STS, needing complex and huge movement constraints, can show a critical step toward comprehending visual rehabilitative programs and interventions to improve physical functioning. Here, we aimed to analyze the coordination of the ankle, knee, hip, and trunk during STS (on both the D and ND sides) among CB, EC, and eyes open (EO) individuals. In addition, we hypothesized that the EC group would show a larger CoC of the ankle and hip than the CB group would.
2. Methods 2.1. Subjects Forty-five female children were recruited to participate in this study. The CB group included 15 females who had congenital blindness. The remaining 30 females were healthy and did not have any visual impairments. These 30 healthy individuals were divided into two different experimental condition groups. The participants in the EC group closed their eyes for 20 min before the STS test, while the subjects in the EO group kept their eyes open. The blind females were physically active in daily life and merely suffered from blindness. The eligibility criteria were to be female, be aged between 84 and 108 months, have no history of musculoskeletal or neuromuscular dysfunction such as flat feet or droop-
ing shoulders, have a BMI between 13 and 20 kg/m2 and be physically active in daily life. The participants were excluded if they presented any history of a ligament injury, surgery in either of the lower extremities, feelings of fatigue, a history of regular athletic training, the inability to complete the research protocol, a recent history of growth spurts that could affect the results, and participation in heavy physical tasks or exercise during the past two days. The dominant foot was determined to be the foot that was used to kick a ball. The study was approved by the local ethics committee (IR.ARUMS. REC.1396.259). 2.2. Data collection procedures Before performing the tests, the methods of using all of the equipment and instruments were demonstrated with a verbal explanation to the participants in the EO group and through the sense of touch for the EC and CB groups. The participants sat barefoot on a firm chair with no armrest, back support or wheels. The height of the chair was adjusted to 100% of each subject’s leg length, which was measured as the distance from the lateral femoral condyle to the ground. The participants sat with their bodies and lower extremities placed symmetrically relative to the chair, and the anterior-superior-iliac-spine (ASIS) width was determined as the distance between the feet. The subjects were instructed to raise their entire bodies from the chair at a selfselected velocity and to remain standing after reaching the upright position for 3 to 4 s (Kerr et al., 1994) with their arms folded across their chests. Each participant was asked to perform five STS trials, with 30 s of rest between trials, after having practiced three times before the recorded trials. Three events defined the STS task: (1) the initiation (In) of the movement, which was when the border of the acromion process marker moved forward in the sagittal plane, (2) the seat-off (SO) event, which was when knee extension began, and (3) the end (Ed) of STS, which was defined by the maximum height of the shoulder marker. According to these events, there were two phases: the preparation phase and the standing phase. Subjects’ joint kinematics were captured using an eight-camera 3D motion capture system, optoelectronic system (Qualisys AB, Sweden), with a sampling frequency of 100 Hz. The motion capture data were filtered using a fourth-order Butterworth filter with a cutoff frequency of 10 Hz by using MATLAB R2015a software. The kinematic values were recorded along the vertical (Z), mediolateral (Y), and anteroposterior (X) directions. The positive sagittal (anterioposterior) axis was the direction of the forward movement, and the positive frontal (mediolateral) axis was directed to the ND side while the positive vertical axis was directed upward. Retroreflective markers were placed over bony landmarks, including the vertex, seventh-cervical-vertebra (C7), and the spinous process of the twelfth-thoracic-vertebrae. Markers were also placed bilaterally on the lateral borders of the acromion process, greater humeral tubercle, olecranon process of the ulna, head of the styloid process of the ulna, ASIS, posterior-superior-iliac-spine (PSIS), greater trochanter, lateral femoral epicondyle, lateral malleolus, 5th metatarsal head, and calcaneal tuberosity. Markers on the olecranon process of the ulna and head of the styloid process of the ulna were used to monitor the arms folded across the chest. Seven segments were defined to create biomechanical models by retroreflective markers. The markers used on lateral malleoli, 5th distal metatarsal head, and calcaneal tuberosity for build ankle (bilaterally). The markers used on center of the foot and the lateral femoral epicondyle for build the knee (bilaterally). The markers used on center of the leg and the center of the pelvis created by the ASIS, PSIS, and greater trochanter for build the hip (bilaterally). The markers on midpoint of the two pelvis and the midpoint of the
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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two shoulder markers (lateral border of the acromion process and head of the humerus) for build the trunk.
ai ¼
The outcome variables were coordination of the ankle, knee, hip, and trunk in the frontal and sagittal planes during four STS cycles. In this study, a vector coding technique (Robertson et al., 2014) was used to quantify coordination of the ankle, knee, hip, and trunk. The coupling angle h, or the relative motion between two segments, was used to calculate the orientation of consecutive frames on the angle-angle diagram (Fig. 4 shows the angle-angle diagram of a normal subject during STS) relative to the right horizontal:
ð1Þ
where 0° h 360°, i indicates consecutive data points in a cycle, and j identifies the four STS cycles. Four angle-angle diagrams over each STS were constructed with (1) the ankle angle on the a-axis and the knee, hip, and trunk angles on the b-axis, (2) the knee angle on the a-axis and the hip and trunk angles on the b-axis, and (3) the hip angle on the a-axis and the trunk angle on the b-axis. Since these angles are directional and obtained from polar distributions (0°-360°), taking the arithmetic mean of a series of angles can result in errors in the average value and incorrect representation of the orientation of the vectors by the average val-
2 1 2 2 ri ¼ bi þ ai
ues. Therefore, mean coupling angles (hi ) must be computed using
circular statistics. hi is calculated within a subject and then across a group from the mean horizontal (bi ) and vertical (ai ) components:
n 1X cos hj;i n j¼1
ð2Þ
ð4Þ
Moreover, it has a well-defined angle with respect to the positive horizontal axis. This angle is referred to as the coupling angle h. The mean coupling angle across the four STS cycles is again defined:
hi ¼
8 > > > <
tan1
ai
if X i > 0
bi
> > 1 > : 180 þ tan
ai
ð5Þ
if X i < 0
bi
The vector coding analysis can provide a measure of the coordination pattern. A vector angle has a value ranging from 0° to 360°. Fig. 1 shows what the vector angles of the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, hip-trunk, D ankle-ND ankle, D knee-ND knee, and D hip-ND hip indicate when they appear in each of the quadrants during STS. Additionally, descriptions of the coordination patterns in terms of 0, 45, 90, 135, 180, 225, 315, and 360 degrees of the above mentioned variables are shown in Fig. 2 (sagittal plane) and Fig. 3 (frontal plane) (see Fig. 4). The CoC (Yen et al., 2017) was calculated as:
!
CoC ¼ r i 1
bi ¼
ð3Þ
The length of the mean vector is then defined as
2.3. Outcome variables and data analysis
aj;iþ1 aj;i hj;i ¼ tan1 bj;iþ1 bj;i
n 1X sin hj;i n j¼1
rðmaxriðri ÞÞ rmax
ð6Þ
where max (ri) is the maximum vector length for the maximum possible vector length observed at each respective interval over the four selected STS cycles, r is the standard deviation, and rmax was calculated using the following formula:
rmax
1 ¼ 2
rffiffiffiffiffiffiffiffiffiffiffiffiffi N N1
ð7Þ
Fig. 1. Relationship between phase angle in each quadrant and ankle-knee (A and J), ankle-hip (D and M), ankle-trunk (G and P), knee-hip (B and K), knee-trunk (E and N), hip-trunk (H and Q), D ankle-ND ankle (C and L), D knee-ND knee (F and O), and D hip-ND hip (I and R) relative motion in sagittal (A, B, C, D, E, F, G, H, and I) and frontal (J, K, L, M, N, O, P, Q, and R) planes. Abbreviations: D, dominant side; ND, nondominant side; LFR, lateral flexion to the right; LFL, lateral flexion to the left.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Fig. 2. Description of the coordination pattern values in each quadrant and movement of segments (ankleknee (A), ankle-hip (B), ankle-trunk (C), knee-hip (D), knee-trunk (E), hip-trunk (F), D ankle-ND ankle, D knee-ND knee, and D hip-ND hip (G)) relative together during sit-to-stand in sagittal plane. Abbreviations: D, dominant side; ND, nondominant side.
Fig. 3. Description of the coordination pattern values in each quadrant and movement of segments (ankleknee (A), ankle-hip (B), ankle-trunk (C), knee-hip (D), knee-trunk (E), hip-trunk (F), D ankle-ND ankle, D knee-ND knee, and D hip-ND hip (G)) relative together during sit-to-stand in frontal plane. Abbreviations: D, dominant side; ND, nondominant side; LFR, lateral flexion to the right; LFL, lateral flexion to the left.
where N is the number of cycles. Note Eq. (7) is only accurate for an array with an even number of normalized samples. The CoC measures the consistency of relative segment motions in a given limb. A large CoC represents high variability of the STS pattern.
standard deviation of groups. In addition, we interpreted the effect size as trivial (d < 0.2), small (0.2 to <0.5), moderate (0.5 and <0.8), or large (0.8). 3. Results
2.4. Statistical analysis A multivariate-analysis-of-variance (MANOVA) test with Bonferroni’s post hoc test was used for between-group comparisons. Additionally, ‘‘P” stands for MONOVA, and ‘‘p” stands for a significant interaction between group and condition. The alpha level was set at p < (0.05/number of parameters). Statistical analysis was performed using SPSS 19.0Ò software. The effect sizes (d) were calculated as a ratio of the mean difference divided by the mean to the
There were no significant differences between the groups in age, mass, height, leg length, and ASIS width (Table 1). On both sides, the vector-angle values of the ankle-knee, anklehip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk pairs for all groups were similar in the sagittal (P = 0.610) and frontal (P = 0.670) planes during all events (Table 2). The CoC of the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk pairs in the sagittal plane showed a
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Fig. 4. The angle-angle diagram (ankle-knee (A and J), ankle-hip (D and M), ankle-trunk (G and P), kneehip (B and K), knee-trunk (E and N), hip-trunk (H and Q), D ankle-ND ankle (C and L), D knee-ND knee (F and O), and D hip-ND hip (I and R)) of a normal subject during sit-to-stand in sagittal (A, B, C, D, E, F, G, H, and I) and frontal (J, K, L, M, N, O, P, Q, and R) planes. Abbreviations: D, dominant side; ND, nondominant side.
Table 1 Demographic characteristics of subjects. Groups
N Mass (kg) Height (m) BMI Leg length (cm) ASIS width (cm) Age (month) Gender Foot dominant side Hand dominant side
Sig.
Congenital blindness
Eyes closed
Eyes open
15 25.6 (2.0) 1.3 (0.0) 16.0 (2.5) 36.5 (1.6) 17.8 (1.1) 94.6 (5.6) Female Right Right
15 24.2 (1.3) 1.1 (0.0) 15.7 (0.8) 34.6 (1.1) 15.7 (0.5) 93.8 (5.9) Female Right Right
15 26.1 (5.1) 1.3 (0.0) 16.0 (2.0) 36.2 (1.5) 16.5 (0.9) 95.8 (5.4) Female Right Right
NA 0.641 0.632 0.912 0.100 0.250 0.856 NA 0.756 NA
Values are mean (standard deviation). Abbreviations: N, number of subjects; NA, not applicable; BMI, body mass index; ASIS, Anterior superior iliac spine.
significant interaction between group and condition at the SO (P = 0.000) and Ed (P = 0.000) events. Hip-trunk CoC (p = 0.002, d = 0.95) on the D side and ankle-hip CoC (p < 0.001, d = 2.18) on the ND side were significantly lower in the CB group than in the EO group at the SO. The ankle-trunk and knee-trunk CoCs were significantly greater in the EC group than in the CB group on the D (p < 0.001, d = 3.40; p < 0.001, d = 3.30) and ND (p < 0.001, d = 3.39; p < 0.001, d = 3.30) sides during the Ed. On the ND side, the EC group presented a greater hip-trunk CoC than the CB group at the Ed (p = 0.029, d = 3.07). Additionally, the CoC in the frontal plane demonstrated a significant interaction between group and condition at the In (P = 0.000), SO (P = 0.000), and Ed (P = 0.000) events. The knee-trunk CoC of the EC group was significantly lower than that of the EO group on the D (p < 0.001, d = 2.10) and ND (p = 0.003, d = 1.61) sides at the In. On the D side, the EC group presented a greater ankle-hip CoC than the CB group at the SO (p < 0.001, d = 2.60). On the ND side, the ankle-knee (p = 0.003, d = 1.67) and ankle-hip (p = 0.002, d = 1.76) CoCs in the EC group were significantly lower than those in the EO group at the Ed. The ankle-knee CoC in the CB group was significantly less than that in the EO group (p = 0.001, d = 1.76). Other variables on both sides were similar among the groups at all events (Table 3). The ankle-knee vector angle in the sagittal plane demonstrated a significant interaction between group and condition in the standing phase (P = 0.015). On the ND side, the ankle-knee vector angle
of the CB group was significantly lower than that of the EO group (p < 0.001, d = 1.48) (Fig. 5B). The CoC measures in the sagittal plane showed a significant interaction between group and condition in the preparation phase (P = 0.002). The ankle-hip CoC of the CB group was significantly lower than that of the EO group (p = 0.003, d = 1.43) on the ND side (Fig. 5F). Furthermore, the knee-trunk CoC in the frontal plane demonstrated a significant interaction between group and condition in the standing phase (P = 0.000). On the D side, the knee-trunk CoC in the CB group was significantly greater than that in the EO group (p < 0.001, d = 1.60) (Fig. 5G). Other variables on both sides were similar among the groups (Fig. 5A, C, D, E, and H). The D ankle-ND ankle, D knee-ND knee, and D hip-ND hip vector angles (Fig. 6A and B) in both planes were similar among the groups. The D hip-ND hip CoC in the sagittal plane demonstrated a significant interaction between group and condition in the preparation phase (P = 0.005). D hip-ND hip CoC in the CB group was significantly less than that in the EO group (p = 0.011, d = 1.08) (Fig. 6C). Additionally, the D knee-ND knee and D hip-ND hip CoCs in the frontal plane showed a significant interaction between group and condition at the In event (P = 0.007) and in the standing phase (P = 0.004), respectively. The D knee-ND knee CoC in the EC group was significantly less than that in the EO group (p = 0.009, d = 1.42) at In. The D hip-ND hip CoCs for the CB group (p = 0.003, d = 1.27) and EC group (p = 0.001, d = 1.26) were
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Table 2 Congenitally blind (CB), eyes closed (EC), and eyes open (EO) children’s ankle-knee (AK), ankle-hip (AH), ankle-trunk (AT), knee-hip (KH), knee-trunk (KT), and hip-trunk (HT) coordination patterns in the sagittal and frontal planes during initiation (In), seat-off (SO), and end (Ed) events in dominant (D) and non-dominant sides. Side
Group
Sagittal plane D CB
EC
EO
ND
CB
EC
EO
Frontal plane D CB
EC
EO
ND
CB
EC
EO
Event
Vector angle (deg) AK
AH
AT
KH
KT
HT
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
166.9 (108.2) 126 (48) 240 (2.2) 156.6 (112.6) 107.1 (47.3) 241.5 (1.3) 162 (102.2) 117.4 (38.4) 240.9 (1.4) 118.6 (70.3) 103.6 (23) 240.4 (1.6) 142.7 (112.2) 115.2 (30.3) 240.8 (1.9) 109.8 (91.9) 136.8 (48.6) 240.6 (0.9)
271.9 (20) 186.5 (78.3) 236.6 (11.6) 250.4 (70.5) 232.8 (72.5) 240.3 (7.5) 271.6 (26.1) 238.1 (51.7) 241.7 (1.3) 248.5 (55.5) 172.2 (81.7) 235.4 (16.4) 264.8 (40.8) 223.8 (63.7) 240.4 (2.2) 259.4 (46.2) 237 (51.2) 240.8 (1.4)
109.2 (67.2) 121.8 (64.5) 172 (45) 109.1 (65.7) 109 (68.9) 135.5 (2.3) 113.8 (68.4) 110.8 (35.9) 159.1 (40.7) 114.6 (66.8) 130.4 (68) 170.9 (45.6) 92.5 (35.1) 118 (66.7) 136.3 (2.7) 112.5 (64.9) 109.7 (28.6) 160.6 (40.6)
275 (13.1) 179.4 (138.2) 222.2 (10.3) 268.9 (42.5) 218.6 (127.1) 224 (7.1) 272.7 (12.5) 261.4 (85) 225.8 (0.7) 264.1 (53.7) 145.6 (136.1) 221.1 (13) 259.4 (50.8) 245.3 (116) 224.3 (1) 264.5 (53.3) 258.5 (79.4) 225 (1.4)
111.1 (65.2) 93 (101.6) 174.1 (29.5) 94.3 (44.1) 87.9 (75.6) 152.1 (1.3) 112.8 (65.1) 91.1 (73.3) 166.8 (26.1) 108.8 (66) 84.6 (102.2) 173.9 (29.1) 100.8 (55) 87.4 (76.4) 152.1 (1.2) 108.9 (65.8) 91.8 (70.5) 167.3 (26)
151.2 (48.3) 127.3 (99.9) 178.6 (35.6) 141.4 (44.4) 132.1 (65.6) 150.9 (8) 152.6 (48) 132.5 (66.8) 166.9 (25.3) 139.8 (58.9) 112.2 (102.7) 173.5 (38) 149.3 (52.2) 129.5 (67.6) 151.7 (1) 145 (53.6) 132.3 (68) 166.9 (25.6)
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
145.9 (103) 125.4 (83.1) 232.7 (4.3) 186.3 (117.3) 111.1 (77.6) 233.2 (4.8) 119.5 (97.6) 127 (82.6) 233 (4.4) 154 (118.8) 158.8 (78.2) 233.9 (4.2) 173.6 (101.2) 169.1 (73.7) 231 (4) 168.1 (116) 189 (101.9) 229.6 (3.4)
176.9 (106.5) 150.8 (98.1) 227.5 (13.5) 228 (102.7) 115.2 (85.4) 229 (11.4) 140.8 (106.2) 135.4 (86) 233 (4.2) 144.1 (118.5) 197.6 (82.2) 229.6 (10.3) 209.5 (103.3) 161.7 (68.7) 230.4 (4.3) 141.2 (114.7) 192.5 (105.5) 229.6 (3.5)
142 (107.2) 147.2 (117.3) 178 (0.9) 177.7 (128.5) 199 (117.3) 177.2 (2.4) 157.6 (133) 141.3 (98.2) 178.1 (0.5) 195.8 (125.2) 193.1 (100.9) 177.9 (1) 198.4 (109.6) 180.2 (82.1) 177.3 (2.6) 180.6 (128.7) 122.1 (92.6) 178.3 (0.4)
150.6 (120.2) 133.7 (112.5) 220.2 (11.5) 174.6 (107.7) 60.4 (60.5) 221.1 (9.6) 130.6 (105.1) 145.8 (105.1) 224.8 (0.5) 155.9 (105.6) 202 (127.1) 221 (9.6) 174.3 (105.9) 108.5 (87.5) 224.3 (1.2) 144.5 (98.4) 129.9 (86.2) 224.8 (0.3)
126.1 (122.5) 131 (133.4) 178.5 (0.6) 161.6 (122.7) 217.7 (153.4) 178.1 (2.7) 150.2 (138.1) 112.4 (113.4) 178.5 (0.3) 166.2 (124) 195.3 (140.1) 178.5 (0.6) 165.3 (114.3) 201.8 (120.8) 177.8 (2.2) 161.6 (122.6) 125.8 (107.2) 178.5 (0.3)
151.2 (117.7) 159.6 (135.3) 177.7 (2.1) 167.1 (98.2) 216.5 (148.9) 176.8 (4.5) 173.6 (139.9) 138 (126.9) 178.5 (0.3) 175.1 (116.2) 161.3 (97.4) 178.1 (1.3) 154.2 (96.9) 195.3 (133) 177.7 (2.6) 190.6 (127) 119.7 (109.3) 178.5 (0.3)
Values are mean (standard deviation).
significantly lower than that of the EO group in the standing phase (Fig. 6D).
4. Discussion The results showed that the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk vector angles for all groups in the sagittal plane on both sides were similar during all events and phases. Compared with healthy children, CB children presented more ankle motion on the ND side in plantar flexion relative to knee motion in extension. The altered ankle-knee vector angle in CB children may be led to the altered COM in these segments. Our previous study (Aylar et al., 2019) detected that COM displacements of the foot and leg were different among groups in the anteroposterior direction. Therefore, altered vector-angle components may be associated with the foot COM and leg COM. Additionally, the CB individuals showed less coordination variability in the sagittal plane than EO subjects at the SO event (hip-trunk on D side and ankle-hip on ND side) and in the preparation phase (ankle-hip on ND side). The SO event is a vital point (the most unstable moment) of STS, where the total load is transferred to the feet and the COM creates an external moment at the knee (Hughes et al., 1994). Moreover, among all segments, the head-arms-trunk (HAT) segment generates the most horizontal momentum of the
whole body-center-of-mass (BCOM), and rotation of the thigh about the knee joint is the main contributor to vertical momentum generation (Riley et al., 1991). Therefore, CB children’s locomotory system may consistently regulate the ankle-hip and hip-trunk coordination as an altered strategy to reduce the possibility of making a movement error when the balance is challenged. In this experiment, the CoCs of the mentioned parameters in the EO group were higher than those in the other groups. These results suggest that healthy individuals have more movement variability. Then, reducing variability is a possible strategy to reduce errors in movement, and this strategy is optimal for the CB group; however, less variability is not necessarily a favorable movement strategy. Furthermore, the EC group demonstrated higher coordination variability than the CB group at Ed (ankle-trunk and knee-trunk on both sides and hip-trunk on the ND side). The CB children’s locomotor systems were able to perform the STS under the deprivation of visual input for 94 months, but EC children only had deprivation of visual input for 20 min. Long-term deprivation of visual input may be influenced by an individual’s habitual activity, so it is reasonable that CB children had more limitations to their activity than did others. This concept can explain why the EC group had higher coordination variability than the CB group in the sagittal plane. The CB group increased their consistency to better control their balance during the challenging task, but the EC group did not adopt this strategy to decrease errors in their STS performance. This result
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Table 3 Coordination variability in different STS events in the sagittal and frontal planes for Congenitally blind (CB), eyes closed (EC), and eyes open (EO) groups in dominant (D) and nondominant (ND) sides. Side
Sagittal plane D
Group
CB
EC
EO
ND
CB
EC
EO
Frontal plane D
CB
EC
EO
ND
CB
EC
EO
Event
Coefficient of correspondence (CoC) AK
AH
AT
KH
KT
HT
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
0.4 (0.3) 0.7 (0.3) 1 (0) 0.4 (0.3) 0.7 (0.2) 1 (0) 0.4 (0.3) 0.8 (0.3) 1 (0) 0.5 (0.2) 0.9 (0.1) 1 (0) 0.3 (0.2) 0.8 (0.2) 1 (0) 0.5 (0.3) 0.7 (0.4) 1 (0)
1 (0.1) 0.2 (0.3) 1 (0) 0.9 (0.2) 0.3 (0.3) 1 (0) 0.9 (0.1) 0.7 (0.4) 1 (0) 0.8 (0.4) 0.1 (0.2)* 1 (0.1) 0.8 (0.4) 0.5 (0.4) 1 (0) 0.8 (0.4) 0.7 (0.3) 1 (0)
0.8 (0.4) 0.7 (0.4) 0.7 (0.2) 0.9 (0.2) 0.7 (0.3) 1 (0)** 0.6 (0.5) 0.8 (0.3) 0.8 (0.2) 0.7 (0.4) 0.7 (0.4) 0.6 (0.2) 0.8 (0.3) 0.9 (0.2) 1 (0)** 0.6 (0.5) 0.9 (0.2) 0.8 (0.2)
1 (0) 0.5 (0.3) 1 (0) 0.8 (0.3) 0.7 (0.2) 1 (0) 1 (0) 0.7 (0.3) 1 (0) 0.8 (0.4) 0.5 (0.2) 1 (0) 0.8 (0.4) 0.7 (0.3) 1 (0) 0.8 (0.4) 0.6 (0.4) 1 (0)
0.8 (0.4) 0.7 (0.2) 0.8 (0.1) 0.8 (0.4) 0.9 (0.1) 1 (0)** 0.6 (0.5) 0.9 (0.1) 0.9 (0.1) 0.8 (0.4) 0.8 (0.2) 0.8 (0.1) 0.8 (0.3) 0.9 (0.1) 1 (0)** 0.6 (0.5) 0.8 (0.2) 0.9 (0.1)
0.8 (0.3) 0.5 (0.3)* 0.8 (0.2) 0.8 (0.4) 0.7 (0.3) 1 (0) 0.7 (0.4) 0.8 (0.3) 0.9 (0.1) 0.7 (0.3) 0.5 (0.2) 0.8 (0.2) 0.8 (0.4) 0.7 (0.3) 1 (0)** 0.6 (0.4) 0.7 (0.4) 0.9 (0.1)
In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed In SO Ed
0.5 (0.3) 0.5 (0.3) 1 (0) 0.3 (0.2) 0.6 (0.3) 1 (0) 0.6 (0.3) 0.4 (0.3) 1 (0) 0.5 (0.4) 0.4 (0.3) 0.9 (0)* 0.4 (0.4) 0.5 (0.3) 0.9 (0)* 0.5 (0.3) 0.3 (0.2) 1 (0)
0.4 (0.4) 0.2 (0.1) 1 (0.1) 0.4 (0.3) 0.6 (0.2)** 1 (0) 0.6 (0.3) 0.4 (0.3) 1 (0) 0.5 (0.4) 0.4 (0.3) 1 (0) 0.6 (0.4) 0.5 (0.4) 0.9 (0)* 0.5 (0.4) 0.2 (0.2) 1 (0)
0.5 (0.4) 0.3 (0.4) 1 (0) 0.3 (0.3) 0.2 (0.1) 1 (0) 0.5 (0.4) 0.4 (0.4) 1 (0) 0.5 (0.4) 0.2 (0.4) 1 (0) 0.4 (0.4) 0.5 (0.4) 1 (0) 0.5 (0.4) 0.1 (0.2) 1 (0)
0.4 (0.3) 0.7 (0.3) 1 (0) 0.4 (0.4) 0.8 (0.4) 1 (0) 0.6 (0.3) 0.4 (0.3) 1 (0) 0.1 (0.1) 0.5 (0.2) 1 (0) 0.3 (0.3) 0.4 (0.4) 1 (0) 0.3 (0.4) 0.4 (0.4) 1 (0)
0.4 (0.4) 0.8 (0.4) 1 (0) 0.2 (0.2)* 0.8 (0.4) 1 (0) 0.7 (0.3) 0.4 (0.4) 1 (0) 0.2 (0.2) 0.4 (0.4) 1 (0) 0.1 (0.1)* 0.3 (0.4) 1 (0) 0.5 (0.4) 0.5 (0.4) 1 (0)
0.3 (0.4) 0.4 (0.4) 1 (0) 0.4 (0.3) 0.7 (0.3) 1 (0) 0.4 (0.4) 0.4 (0.4) 1 (0) 0.2 (0.1) 0.3 (0.4) 1 (0) 0.4 (0.4) 0.4 (0.4) 1 (0) 0.3 (0.4) 0.3 (0.4) 1 (0)
Values are mean (standard deviation). Abbreviations: AK, ankle-knee; AH, ankle-hip; AT, ankle-trunk; KH, knee-hip; KT, knee-trunk; HT, hip-trunk; In, initiation; SO, seat-off; Ed, end; STS, sit-to-stand. * When compared to the eyes open group (p < 0.05). ** When compared to the congenitally blind group (p < 0.05).
suggests that fewer CoCs that were reported were optimal to manage a hard task in CB children. In the frontal plane, the ankle-knee, ankle-hip, ankle-trunk, knee-hip, knee-trunk, and hip-trunk vector angles of all groups were similar. This result indicates that the ankle, knee, hip, and trunk move harmoniously in the frontal plane during STS, and short- or long-term restriction of visual input does not influence these parameters. However, the EC group had less variability relative to the EO group at the In (knee-trunk on both sides) and Ed (ankle-knee and ankle-hip on ND side) events. A previous study demonstrated that less ankle-hip coordination variability is associated with chronic-ankle-instability (CAI) in the frontal plane (Yen et al., 2017), and the authors assumed it to be a preventative strategy for reducing future injuries of involved segments and controlling balance among subjects with CAI. The knee initiates movement at the In event, so the reductions in the knee-trunk and ankle-knee CoCs suggest that these segments maintain their consistency to start STS successfully. Moreover, the ankle-hip pair of the EC group showed great coordination variability compared to that of the CB group on the ND side during SO. This condition was explained for the sagittal plane, but unfortunately, there are a limited number of studies on the CoC in the frontal plane. Compared with the EO group, the CB group presented high variability of the
knee-trunk pair on the D side in the standing phase. However, at Ed, the CB group had less variability in the ankle-knee pair on the ND side. The results suggested that long-term restricted visual memory has a significant impact on knee-trunk coordination during the standing phase and may predispose individuals to future injuries of the involved limbs. On the other hand, the low ankleknee CoC of the CB group was a preventative strategy to avoid injuries. Comparing the D and ND sides, the vector angle and CoC of the ankle, knee, and hip in the sagittal plane were similar, suggesting good bilateral coordination of the lower extremity during STS, although there was time-restricted visual input for subjects. However, during the preparation phase, the D hip-ND hip CoC of the CB group was lower than that of the EO group. The interlimb adaptations in hip segments of CB children indicated that long-term restricted visual memory has led to consistency among subjects. Generally, a difference in interlimb variables is a consequence of an injury (Haddad et al., 2006). The motor control system of CB children may alter the coordination between the individual limbs to adapt to the long-term restricted visual condition. Also, the presented results in the study can be different for male children (Bates et al., 2016; Bruening et al., 2015; Jenkins et al., 2017), but it deserves more investigations.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
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Fig. 5. Coordination pattern (A, B, C, and D) and coordination variability (E, F, G, and H) in sagittal (A, B, E, and F) and frontal (C, D, G, and H) planes on dominant (A, C, E, and G) and non-dominant (B, D, F, and H) sides among the congenitally blind, eyes closed, and eyes open groups during preparation phase (PP) and standing phase (SP). Bars represent standard deviations. *: When compared to the eyes open group (p < 0.05).
The vector angles and CoCs of the D side of the lower limb joints with its ND sides in the frontal plane were similar among individuals during events. The exceptions were the lower D knee-ND knee CoC of the EC group at In and the lower D hip-ND hip CoCs of the EC and CB groups than those of the EO group in the standing phase. They indicated that bilateral consistency occurred in the hip of the CB group in the standing phase and in the knee and hip of the EC group at the In event and in the standing phase, respectively. We were not able to find other studies addressing these issues. In general, the results showing that the human body continuously tries to reach optimal coordination. Finally, the restricted
visual input was shown to have considerable influence on the coordination pattern in the standing phase and on coordination variability at all events and phases. These results indicate that visual memory cannot change the coordination pattern of the STS, but the coordination variability of this movement is highly influenced by the duration visual data is restricted. The number of subjects in the present investigation was relatively small; however, this study had sufficient statistical power to detect between-group differences. Further studies are suggested to combine the values of joint torques with muscle activities during STS.
Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708
M.F. Aylar et al. / Journal of Biomechanics xxx (xxxx) xxx
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Fig. 6. The control and experimental groups’ D ankle-ND ankle, D knee-ND knee, D hip-ND hip coordination pattern (A and B) and variability (C and D) in the sagittal (A and C) and frontal planes (B and D) in all events and phases of sit-to-stand. Bars represent standard deviations. Abbreviations: D, dominant side; ND, non-dominant side; In, initiation; SO, seat-off, Ed, end; PP, preparation phase; SP, standing phase. *: When compared to the eyes open group (p < 0.05).
5. Conclusion The results of this study indicated that the consolidation process occurred not only for trunk but also for the lower extremities. In the sagittal plane, the CB individuals presented difficulties in the ankle-knee coordination pattern parameters on the nondominant side (at standing phase). In this plane, their dominant side of hip-trunk (at seat-off), and nondominant side of ankle-hip (at seat-off and in the preparation phase); in the frontal plane, their nondominant side of ankle-knee (at the end) coordination variability parameters were less than the EO group. However, they had greater knee-trunk coordination variability relative to the EO group on the dominant side during the standing phase in the frontal plane. Hence, this investigation recommends that the design of rehabilitation programs should focus on the amendment of blind individuals’ strategies to prevent future injuries among them. Acknowledgments We thank all of the individuals who participated in the study. References Aylar, M.F., Dionisio, V.C., Jafarnezhadgero, A., 2019. Do the center of mass strategies change with restricted vision during the sit-to-stand task?. Clin. Biomech. 62, 104–112. https://doi.org/10.1016/j.clinbiomech.2019.01.011. Aylar, M.F., Firouzi, F., Araghi, M.R., 2016. Influence of time restriction, 20 minutes and 94.6 months, of visual information on angular displacement during the sitto-stand (STS) task in three planes. J. Phys. Therapy Sci. 28 (12), 3330–3336. https://doi.org/10.1589/jpts.28.3330. Aylar, M.F., Jafarnezhadgero, A.A., Esker, F.S., 2018. Sit-to-stand ground reaction force characteristics in blind and sighted female children. Gait & Posture 62, 34– 40. https://doi.org/10.1016/j.gaitpost.2018.03.004. Bates, N.A., Nesbitt, R.J., Shearn, J.T., Myer, G.D., Hewett, T.E., 2016. Sex-based differences in knee ligament biomechanics during robotically simulated athletic tasks. J. Biomech. 49 (9), 1429–1436. https://doi.org/10.1016/j.jbiomech. 2016.03.001.
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Please cite this article as: M. F. Aylar, V. C. Dionisio, A. Jafarnezhadgero et al., Body coordination during sit-to-stand in blind and sighted female children, Journal of Biomechanics, https://doi.org/10.1016/j.jbiomech.2020.109708